import java.io.IOException;
import java.net.*;
import java.util.Scanner;

public class UdpEchoClient {

    private DatagramSocket socket=null;

    private String serverIp;
    private int serverPort;

    //和服务器不同.此处的构造方法是要指定访问的服务器地址
    public UdpEchoClient(String serverIp,int serverPort) throws SocketException {
        this.serverIp=serverIp;
        this.serverPort=serverPort;
        socket=new DatagramSocket();   //这里的port让系统自己确定

    }

    public void start() throws IOException {
        while (true){
            Scanner scanner=new Scanner(System.in);
            //1.让用户输入内容
            System.out.println("请输入要发送的内容");
            if(!scanner.hasNext()){
                break;
            }
            String request=scanner.next();
            //2.把请求发送给服务器,需要构造DatagramPacket对象
            //不光要构造载荷,还需要设置服务器的IP和端口号
            DatagramPacket requestPacket=new DatagramPacket(request.getBytes(),request.getBytes().length
                    , InetAddress.getByName(serverIp),serverPort);
            //3.发送数据包
            socket.send(requestPacket);

            //4.接收服务器的响应
            DatagramPacket responsePacket =new DatagramPacket(new byte[4096],4096);
            socket.receive(responsePacket);
            //5.从服务器读取数据进行解析
            String response=new String(responsePacket.getData(),0,responsePacket.getLength());
            System.out.println(response);
        }
    }

    public static void main(String[] args) throws IOException {
        UdpEchoClient client=new UdpEchoClient("127.0.0.1",9090);
        client.start();
    }
}
